Interior Lamps Dimming

WARNING: This page is about a different car, the 2019 Buick Cascada, 2018 Buick Cascada, and 2017 Buick Cascada. However, it is still accessible from the selected car via links, so may be relevant.

The second group includes lamps which may be dimmed. This group may use a combination of light emitting diodes (LED), incandescent lamps, and pulse width modulation (PWM) illumination.

Cigarette lighter receptacle
Dome/reading lamps - front
Folding top/global window switch
Headlamp switch
HVAC controls
Instrument cluster
Multifunction switch - instrument panel
Multifunction switch 1 - instrument panel
Multifunction switch 2 - instrument panel
Park brake control switch
Radio controls
Seat venting switch - driver
Seat venting switch - passenger
Sport mode switch
Steering wheel controls switch - left
Steering wheel controls switch - right
Theft deterrent sensor disable switch
Tour mode switch
Window switch - passenger

With the headlamp switch in the PARK or HEAD position, the park lamp switch signal circuit provides an input to the body control module (BCM). The BCM responds by applying voltage to the park lamps as well as the backlight dimming control circuits illuminating all components with interior backlighting. All interior backlighting turns ON at the dimming level indicated by the instrument panel dimmer switch. The instrument panel dimmer switch is a momentary type switch and utilizes a resistor ladder to increase and decrease the brightness of the interior backlighting components. The instrument panel dimmer switch provides a voltage signal to the BCM that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The BCM provides a low reference signal and a B+ circuit to the instrument panel dimmer switch. When the instrument panel dimmer switch is held in the desired position, the dimmed voltage setting is applied from the instrument panel dimmer switch through the instrument panel dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies a pulse width modulated (PWM) voltage through the backlighting control circuits illuminating the interior backlighting to the requested level of brightness.

The backlighting for the HVAC controls, instrument cluster, and radio controls are controlled by the BCM via serial data. When the instrument panel dimmer switch is operated to the desired backlighting setting, the BCM sends a serial data message to the HVAC control module, radio, and instrument cluster requesting the backlighting be adjusted to the desired level.